but when i put in the empty 700 MB cd and set the 730 MB BIN image file to burn , it goes over the red line in nero, will it still fit?

I answered your question... so did everyone else, if its vcd or svcd porn movie, then it can be 800 megs and fit on a CD... if its a data CD, then you will be overburning and I don't know if your drive / media will support it

but when i put in the empty 700 MB cd and set the 730 MB BIN image file to burn , it goes over the red line in nero, will it still fit?

I'm assuming this BIN file is a cdrom image. If yes, then if there's a cue file that accompanies it, you select Burn Image from either the File or Record menu of Nero. You don't drag and drop it in a new cd compilation.